It has been well known that static electricity of electrified optical display device can deteriorate or can even damage built-in electronic components. For example, electronic components built in a liquid crystal panel include field effect transistors such as TFT elements. In order to prevent electrostatic discharge damage of such electronic components, manufacturing of liquid crystal display devices is normally completed after processes described in the following.
In general, a liquid crystal panel has a structure where a liquid crystal layer is encapsulated between a color filer layer (CF substrate) and a transparent electrode layer (TFT substrate). A liquid crystal display device is finished at least after a process of laminating rectangularly-shaped polarizing film sheets to both surfaces of a liquid crystal panel. At this process, in RTP lamination method and apparatus which is different from conventional sheet lamination (sheet-type lamination) method and apparatus, when a polarizing film sheet is peeled from a carrier film, static electrification is caused in the carrier film, and on the other hand, the polarizing film sheet including an adhesive layer which is simultaneously statically electrified by peeling is laminated to a liquid crystal panel while peeling off from the carrier film.
Conventional lamination method and apparatus, in general, comprises steps of preparing many optical film sheets and accumulating them in a magazine, feeding an optical film sheet one by one, peeling a releasable film sheet from a polarizing film sheet having an adhesive layer with the releasable film sheet, and positioning and laminating a separately-conveyed liquid crystal panel to the exposed adhesive layer of the polarizing film sheet, and since a liquid crystal panel is laminated at a predetermined lamination position to a polarizing film sheet which is previously peeled and the peeled releasable film sheet is processed without approaching to the predetermined lamination position, the releasable film sheet does not affect to the liquid crystal panel to be laminated to a polarizing film sheet even if it is statically electrified by peeling.
Thus, a remaining problem is how to attenuate static charge of a polarizing film sheet including an adhesive layer statically electrified by peeling, before laminating to a liquid crystal panel. Various attempts have been made to address the problem.
RTP lamination method and apparatus comprise a process of peeling a polarizing film sheet including an adhesive layer from a carrier film and simultaneously laminating the polarizing film sheet including the adhesive layer to a liquid crystal panel. More in particular, in RTP lamination method and apparatus, since a liquid crystal panel is conveyed to a predetermined lamination position in close vicinity of a peeled carrier film where a polarizing film sheet including an adhesive layer is laminated to the liquid crystal panel while being peeled from the carrier film, it is not possible to avoid effect of the carrier film and the polarizing film sheet that are statically electrified by peeling. Inductive electrification of a liquid crystal panel due to static electrification caused by peeling was not considered in conventional lamination method and apparatus and is clarified as a new technical problem to be solved only in RTP lamination method and apparatus.
That is, at least two problems need to be solved to prevent static electrification of a liquid crystal panel in RTP lamination method and apparatus. A first problem is to prevent inductive electrification of a liquid crystal panel induced by a carrier film, being conveyed in close vicinity of the carrier film which is statically electrified by peeling. A second problem is how to address inductive electrification of the liquid crystal panel caused when laminating thereto a polarizing film sheet including an adhesive layer which is statically electrified while peeling from the carrier film. If it is addressed incompletely, electronic components built-in an inductively-electrified liquid crystal panel may be damaged by static electricity, or even if not damaged, light leaking parts due to orientation disorder of liquid crystal may be found in an inspection process in a completed liquid crystal display device, as seen in a photograph in FIG. 2. As a result, a transmission inspection of a liquid crystal display device as a product becomes difficult which in turn compromises continuous manufacturing of a liquid crystal display device.
Various proposals have been made for conventional technical problems. For example, Patent Document 1 describes an optical film laminate which can restrict affect of static electricity caused by peeling. More in particular, a conductive layer is provided on a surface for forming an adhesive layer of an optical film configuring an optical film laminate. Patent Document 2 also describes as that an inductive adhesive layer is formed on an optical film laminate. Further, Patent Document 3 describes as that inductivity is provided to a continuous web of optical film to be used for example in a surface protection film sheet for protecting a polarizing film sheet used, after being laminated to a liquid crystal panel configuring an optical film laminate, in a manufacturing process of an optical display device. Patent Document 4 describes as that static electrification of an optical film laminate caused by peeling from a releasable film is controlled by intervening a conductive layer formed with sheet resistance of 102 Ω/sq or higher and 106 Ω/sq or less in the optical film laminate.
Patent Document 5 describes a lamination method and an apparatus for continuously manufacturing optical display devices by restricting static electricity caused by peeling in optical film sheets to be laminated to panel components. More in detail, Patent Document 5 relates to a lamination method and an apparatus for continuously manufacturing optical display devices with a continuous web of optical film laminate configured with a base film which corresponds to a carrier film and a functional film which corresponds to an optical film, including that functional film sheets are formed from a functional film, the functional film sheets are peeled with a peeling means from a base film i.e. a carrier film of the continuous web of optical film laminate, and the functional film sheets are laminated to the panel components.
Patent Document 5 further describes a lamination method and an apparatus in which a peeling means is configured with a material positioned on further negative side (or further positive side) in triboelectric series than a carrier film when a continuous web of carrier film is negatively (or positively) charged by peeling, so that static electricity generated in functional film sheets when peeling from the continuous web of carrier film does not electrically damage electrical components built in panel components when manufacturing optical display devices by laminating the functional film sheets to the panel components. Patent Document 5 describes as that static electric charge generated in a carrier film is controlled and thereby electric charge in functional film sheets is restricted by selecting a material of a peeling means according to a state of static electrification, i.e. degree of negative (or positive) charge, of the carrier film caused by peeling, which is, in short, that electric charge of the functional film sheets to be directly laminated to the panel components is restricted.